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. May/Jun 2018;37(3):241-262.
doi: 10.1177/1091581818766318. Epub 2018 Apr 11.

Safety Evaluation of Soy Leghemoglobin Protein Preparation Derived From Pichia Pastoris, Intended for Use as a Flavor Catalyst in Plant-Based Meat

Free PMC article

Safety Evaluation of Soy Leghemoglobin Protein Preparation Derived From Pichia Pastoris, Intended for Use as a Flavor Catalyst in Plant-Based Meat

Rachel Z Fraser et al. Int J Toxicol. .
Free PMC article


The leghemoglobin protein (LegH) from soy ( Glycine max) expressed in Pichia pastoris (LegH preparation, LegH Prep) imparts a meat-like flavor profile onto plant-based food products. The safety of LegH Prep was evaluated through a series of in vitro and in vivo tests. The genotoxic potential of LegH Prep was assessed using the bacterial reverse mutation assay (Ames test) and the in vitro chromosome aberration test. LegH Prep was nonmutagenic and nonclastogenic in each test, respectively. Systemic toxicity was assessed in a 28-day dietary study in male and female Sprague Dawley rats. There were no mortalities associated with the administration of LegH Prep. There were no clinical observations, body weight, ophthalmological, clinical pathology, or histopathological changes attributable to LegH Prep administration. There were no observed effects on male reproduction in this study, but the suggestion of a potential estrous cycle distribution effect in female rats prompted a second comprehensive 28-day dietary study in female Sprague Dawley rats. This study demonstrated that female reproductive parameters were comparable between rats treated with LegH Prep and concurrent control rats. These studies establish a no observed adverse effect level of 750 mg/kg/d LegH, which is over 100 times greater than the 90th percentile estimated daily intake. Collectively, the results of the studies presented raise no issues of toxicological concern with regard to LegH Prep under the conditions tested.

Keywords: Pichia pastoris; flavor; leghemoglobin; safety; toxicology.

Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Rachel Z. Fraser, Puja Agrawal, and Sue Klapholz are employees of Impossible Foods Inc.

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